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Early Season Insects of Soybean

Early season insects of soybean feed on seeds and seedlings causing plant injury, stunting, delayed emergence, or stand loss.

Scouting is necessary to determine the types of insects present and their population densities in order to make informed management decisions.

Sampling methods include scouting, soil sampling, and using baited traps.

Be on the Lookout

Early season soybean insects should be on a grower’s mind when examining seedling emergence and soybean stands this spring. Early season insects of soybean feed on seeds and seedlings causing plant injury, stunting, delayed emergence, or stand loss.

Insects to Look For

Bean leaf beetle (BLB). Adult BLB (Figure 1) are about 1/4 inch in length. The most distinguishing characteristic is the presence of a small black triangle located at the base of the forewings. Some beetles will have four black markings on the wings. Typically, the beetles are dark yellow in color but can range in hues of yellow, orange, and red. Early season injury to soybean is caused by the overwintered adults feeding on cotyledons, leaves, and stems. In addition, this pest can transmit bean pod mottle virus.

Figure 1. Bean leaf beetle on soybean leaf.

Wireworm. Wireworm (Figure 2) can be a problem in soybean, especially in fields previously planted with sod or small grains. Wireworms are hard-bodied, slender, brownish larvae that grow to about 1 inch long. They feed on seeds and seedlings.

Figure 2. Wireworm in soil.

Seedcorn maggot. These maggots are yellowish-white, about 1/4 inch long, and lack a defined head and legs (Figure 3). Seedcorn maggots feed on newly planted soybean seeds and can reduce stands.

White grub. True white grubs and masked chafer grubs can damage soybean seedlings, especially when the soybean crop follows sod or another cover crop. White grubs range in size from 1/4 to over 1 inch long and have white bodies with tan to brown heads (Figure 4). White grub species can be distinguished from one another by the pattern of rasters (bristle-like hairs) on the tip of the abdomen. White grubs feed on plant roots.

Figure 4. White grubs in soil.

Cutworm and armyworm. These caterpillars are generally 1 to 2 inches long. Cutworms are gray, brown, or black in color, and marked with dark spots or lines (Figure 5). Armyworms may vary from green to almost black, often with bright stripes down the body. These worms feed on leaves and stems, often severing the emerging seedling and cotyledons.

Figure 5. Black cutworm.

Soybean aphid (SBA). Soybean aphids are very small (less than 1/16th inch long), soft-bodied, pear-shaped insects (Figure 6). They vary in color from pale yellow to light green with black cornicles on the back of the abdomen. Early season aphid feeding can lead to stunted plants with fewer nodes, which can result in fewer pods.

Figure 6. Soybean aphids on the underside of a trifoliate leaf.

Sampling Methods and Insect Management

Wireworm bait stations. Bury approximately 1/2 cup each untreated wheat and corn seeds 6 inches deep in the soil. To increase soil temperature and facilitate germination, cover the trap with a piece of black plastic covered by a larger piece of clear plastic. Traps should be installed 2 to 3 weeks prior to planting and placed uniformly throughout the field.

Cutworm and armyworm scouting. Beginning with seedling emergence, observe 20 plants in 5 different areas throughout the field for evidence of leaf feeding or cutting and measure the size of the worms. To find larvae during the day, dig 2 to 3 inches into the soil.

Early season soybean aphid scouting. Use a magnifying glass to inspect the undersides of the top most trifoliate leaves where early season aphids are most likely to be found. Check 30 plants in 10 to 20 locations throughout the field on a weekly basis.

Preventative treatments, like seed treatments, may be available to help provide above ground protection from early season BLB and SBA for up to 30 days after planting. After emergence, scouting can help determine if action thresholds are met and insecticide application is warranted. However, treatment action thresholds (Table 1) can vary by state, pest, and stage of crop development. Consult with an Extension entomologist and/or agronomist for local recommendations.

XtendiMax® herbicide with VaporGrip® Technology is part of the Roundup Ready® Xtend Crop System and is a restricted use pesticide. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. It is a violation of federal and state law to use any pesticide product other than in accordance with its labeling. XtendiMax® herbicide with VaporGrip® Technology and products with XtendFlex® Technology may not be approved in all states and may be subject to use restrictions in some states. Check with your local product dealer or representative or U.S. EPA and your state pesticide regulatory agency for the product registration status and additional restrictions in your state. For approved tank-mix products and nozzles visit XtendiMaxApplicationRequirements.com.

Commercialization is dependent on multiple factors, including successful conclusion of the regulatory process. The information presented herein is provided for educational purposes only, and is not and shall not be construed as an offer to sell, or a recommendation to use, any unregistered pesticide for any purpose whatsoever. It is a violation of federal law to promote or offer to sell an unregistered pesticide.

Do not export Roundup Ready® Alfalfa seed or crop, including hay or hay products, to China pending import approval. In addition, due to the unique cropping practices do not plant Roundup Ready® Alfalfa in Imperial County, California, pending import approvals and until Forage Genetics International, LLC (FGI) grants express permission for such planting.

Forage Genetics International, LLC (“FGI”) is a member of Excellence Through Stewardship® (ETS). FGI products are commercialized in accordance with ETS Product Launch Stewardship Guidance, and in compliance with FGI’s Policy for Commercialization of Biotechnology-Derived Plant Products in Commodity Crops. Certain products have been approved for import into key export markets with functioning regulatory systems. Any crop or material produced from this product can only be exported to, or used, processed or sold in countries where all necessary regulatory approvals have been granted. It is a violation of national and international law to move material containing biotech traits across boundaries into nations where import is not permitted. Growers should talk to their grain handler or product purchaser to confirm their buying position for this product. Growers should refer to http://www.biotradestatus.com/ for any updated information on import country approvals. Excellence Through Stewardship® is a registered trademark of Biotechnology Industry Organization.

Monsanto Company is a member of Excellence Through Stewardship® (ETS). Monsanto products are commercialized in accordance with ETS Product Launch Stewardship Guidance, and in compliance with Monsanto’s Policy for Commercialization of Biotechnology-Derived Plant Products in Commodity Crops. This product has been approved for import into key export markets with functioning regulatory systems. Any crop or material produced from this product can only be exported to, or used, processed or sold in countries where all necessary regulatory approvals have been granted. It is a violation of national and international law to move material containing biotech traits across boundaries into nations where import is not permitted. Growers should talk to their grain handler or product purchaser to confirm their buying position for this product. Excellence Through Stewardship® is a registered trademark of Excellence Through Stewardship.

ALWAYS READ AND FOLLOW DIRECTIONS FOR USE ON PESTICIDE LABELING. IT IS A VIOLATION OF FEDERAL AND STATE LAW to use any pesticide product other than in accordance with its labeling. NOT ALL formulations of dicamba or glyphosate are approved for in-crop use with Roundup Ready 2 Xtend® soybeans. ONLY USE FORMULATIONS THAT ARE SPECIFICALLY LABELED FOR SUCH USES AND APPROVED FOR SUCH USE IN THE STATE OF APPLICATION. Contact the U.S. EPA and your state pesticide regulatory agency with any questions about the approval status of dicamba herbicide products for in-crop use with Roundup Ready 2 Xtend® soybeans.

Roundup Ready 2 Xtend® soybeans contains genes that confer tolerance to glyphosate and dicamba. Glyphosate will kill crops that are not tolerant to glyphosate. Dicamba will kill crops that are not tolerant to dicamba. Glufosinate will kill crops that are not tolerant to glufosinate. Contact your Monsanto dealer or refer to Monsanto’s Technology Use Guide for recommended weed control programs.

B.t. products may not yet be registered in all states. Check with your Monsanto representative for the registration status in your state.

IMPORTANT IRM INFORMATION: RIB Complete® corn blend products do not require the planting of a structured refuge except in the Cotton-Growing Area where corn earworm is a significant pest. SmartStax® RIB Complete® corn blend is not allowed to be sold for planting in the Cotton-Growing Area. See the IRM/Grower Guide for additional information. Always read and follow IRM requirements.

Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.

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